Increasingly, consumers are demanding portable devices, such as personal digital assistants (PDA's), MP3 players, portable memory systems, advanced cell phone systems, and cameras. Traditional non-volatile memory storage systems, such as floppy disks, hard drives, and optical drives, are generally unsuitable for use in portable devices because they suffer from mechanical failures, excess weight, large size and high energy consumption. As a result, manufacturers of portable devices are turning to solid-state memory systems, such as flash memory and electrically erasable, programmable read-only memory (EEPROM).
Accessing and storing data on solid-state memory devices, such as flash memory, utilizes virtualized addressing. Solid-state memory devices tend to wear with use and, as such, sectors within a solid-state memory device may lose the capacity to store error free data. To reduce the problem of solid-state memory wear, microcontrollers generally balance usage between sectors of the memory. For example, when data is provided to a flash memory device it may be stored in a first sector and when the data is updated the microcontroller may store the data in a second sector, reducing wear on the first sector. As a result, the physical location of a block of data may change. To facilitate this balancing and to address changing physical addresses, microcontrollers generally create a table that is used to convert location based addresses used by computational systems to the virtual addresses used within the flash memory devices. In this manner, a system may address a set of data using the same location based address while a microcontroller may store that information in changing sectors of the flash memory or at different addresses within the flash memory depending upon the balancing protocols. When a sector turns bad within the flash memory device, the microcontroller may create a mapping of bad data sectors to prevent storage of data in such bad data sectors.
The cataloging of bad sectors and creation of sector maps is typically performed by reading a data sector and checking for particular code values in the system data. Generally, an ECC associated with all of the data of a data sector is included in a data sector for use in correcting and checking for noise in the data. For example, an ECC is calculated based on data when the data is stored and is stored with the data. When the data is accessed, a new ECC is calculated from the data and compared to the ECC stored with the data. If there is a difference between the new ECC and the stored ECC, the data is likely corrupted and the sector may be bad. In many examples, ECCs may be used to correct the data before transmission to subsequent memory systems or processors.
Such error detection, error correction, and cataloging of bad data blocks is of increased importance for multi-level cell flash. Multi-level cell (MLC) flash has a greater storage density than traditional single level cell flash. However, multi-level cell flash typically has higher error rates and may wear faster. As such, error correction and sector cataloging are increasingly useful for non-volatile solid-state memory devices.
However, the process of reading the data, calculating ECCs and correcting corrupted data is a lengthy process. As such, performing tasks, such as mapping data sectors, consumes system resources. In one example, mapping tasks may reduce performance of connected memory buses. As such, there is a need for an improved system and method for reading non-volatile memory.